Birthplace of hurricanes heating up say NOAA scientists
NOAA
May 3, 2006
The region of the tropical Atlantic where many hurricanes originate has warmed by several tenths of a degree Celsius over the 20th century, and new climate model simulations suggest that human activity, such as increasing greenhouse gas emissions into the atmosphere, may contribute significantly to this warming. This new finding is one of several conclusions reported in a study by scientists at the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, N.J., published today in the Journal of Climate.
“This very long-term increase in temperature may seem small but is comparable in magnitude to shorter time-scale, multi-decadal changes that many scientists now believe contribute strongly to an increase in hurricane activity in the Atlantic,” said Thomas Knutson, lead author of the paper and a senior research meteorologist at GFDL. “The challenge is to understand the relative roles of anthropogenic and natural factors in producing these temperature changes—and this study is a step in that direction—and then to determine whether and how these long-term changes in temperature could be affecting Atlantic hurricane activity.”
The region, which extends from 10 degrees N to 20 degrees N in the area of the Cape Verde Islands, has been identified as the origin for a large portion of major hurricanes in the tropical North Atlantic, and is known as the “Main Development Region.” Ocean surface temperatures in this region warmed over the 20th century, roughly tracking the global mean, or average, but this region has greater multi-decadal variability than the global mean does when looking at long-term trends.
The climate model simulations are based on a new state-of-the-art coupled atmosphere-ocean model developed over several years at GFDL. The new simulations include improved representations of a number of environmental factors that can affect climate, such as greenhouse gases, volcanic eruptions, solar variability, land-use changes and atmospheric aerosols, very fine particulate matter in the air. More research is being conducted to improve the representation of these forcings, and of the aerosol effects in particular.
Satellite image for larger view of Hurricane Katrina taken Aug. 28, 2005, at 11:45 a.m. EDT as the storm raged as a Category 5 storm in the Gulf of Mexico, a day before it slammed into the Gulf Coast. Photo courtesy of NOAA. RELATED ARTICLES Global warming causing stronger hurricanes confirms study: The link between warmer ocean temperatures and increasing intensity of hurricanes has been confirmed by scientists at the Georgia Institute of Technology. Last year, two studies published in the journals Nature and Science found a strong correlation between rising tropical sea surface temperatures and an increase in the strength of hurricanes. 2005 had worst weather-related financial losses on record: This year witnessed the largest financial losses ever as a result of weather-related natural disasters linked by many to human action, more than $200 billion compared to $145 billion in 2004, the previous record, according to statistics presented to the United Nations Climate Change Conference currently meeting in Montreal, Canada. US denies hurricane link with climate change: Harlan Watson, chief climate control negotiator for the U.S. State Department, told the Associated Press that the Bush administration does not blame global warming or climate change for extreme weather — including the hurricanes that thrashed the Gulf earlier this year. “There’s a difference between climate and extreme weather,” Watson said. “Our scientists continually tell us we cannot blame any single extreme event, attribute that to climate change.” 2005 Atlantic hurricane season worst on record: The 2005 Atlantic hurricane season is the busiest on record and extends the active hurricane cycle that began in 1995 — a trend likely to continue for years to come. The season included 26 named storms, including 13 hurricanes in which seven were major (Category 3 or higher). Number of category 4 and 5 hurricanes has doubled over 35 years: The number of Category 4 and 5 hurricanes worldwide has nearly doubled over the past 35 years, even though the total number of hurricanes has dropped since the 1990s, according to a study by researchers at the Georgia Institute of Technology and the National Center for Atmospheric Research (NCAR). The shift occurred as global sea surface temperatures have increased over the same period. The research appears in the September 16 issue of Science. Hurricanes getting stronger due to global warming says study: Late last month an atmospheric scientist at Massachusetts Institute of Technology released a study in Nature that found hurricanes have grown significantly more powerful and destructive over the past three decades. Kerry Emanuel, the author of the study, warns that since hurricanes depend on warm water to form and build, global climate change might increase the effect of hurricanes still further in coming years. Hurricane Katrina damage just a dose of what’s to come: The kind of devastation seen on the Gulf Coast from Hurricane Katrina may be a small taste of what is to come if emissions of the greenhouse gas carbon dioxide (CO2 ) are not diminished soon, warns Dr. Ken Caldeira of the Carnegie Institution’s Department of Global Ecology in his opening remarks at the 7th International Carbon Dioxide Conference in Boulder, Colorado, September 26, 2005. If current trends continue, some 5 trillion tons of carbon is expected to be spewed into the atmosphere over the next three centuries from human fossil-fuel burning. It will have serious consequences by warming the planet on average between 7 and 20 degrees Fahrenheit and turning the oceans acidic. Hurricane could hit San Diego: San Diego has been hit by hurricanes in the past and may be affected by such storms in the future according to data from the National Oceanic and Atmospheric Administration (NOAA). While a hurricane in San Diego would likely produce significantly less damage than Hurricane Katrina in New Orleans, it could still exact a high cost to Southern California especially if the region was caught off guard. |
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The new model simulations used current best estimates of a number of historical climate forcings to simulate climate variations over the 20th century. In the Main Development Region, the observed warming during the 20th century is simulated much more realistically in the models that include anthropogenic forcing than in models with only natural effects.
The results suggest that the century-scale warming tendency in the Main Development Region may have been caused largely by anthropogenic forcing, including increases in atmospheric greenhouse gas concentrations.
Other sources of anthropogenic forcing include aerosols and land-use changes. Examples of natural effects are volcanic emissions, long-term variability of solar radiation, and internal variability, such as the internal processes within the climate system.
Atlantic hurricane variability and its causes is the subject of intensive scientific investigations by scientists. Earlier studies suggest that warmer tropical sea surface temperatures can lead to hurricanes of greater intensity. Other studies at NOAA have concluded that warmer sea surfaces is one of several important factors affecting Atlantic hurricane activity. Ongoing research continues to address uncertainties in the observed trend, past climate forcing estimates, internal variability and climate sensitivity.
Other significant conclusions of the new GFDL study include findings that extend beyond the North Atlantic. Simulations of global trends and trends in several other specific regions also produced more realistic results when anthropogenic forcing was included in addition to natural effects. An example is the Indian Ocean and western tropical Pacific, where a regional warming trend has emerged particularly clearly during the past half century. These conclusions support similar findings from earlier studies.
The Geophysical Fluid Dynamics Laboratory advances NOAA’s expert assessments of changes in national and global climate through research, improved models and products. The goal of GFDL’s research is to understand and predict the Earth’s climate and weather, including the impact of human activities.
NOAA, an agency of the U.S. Department of Commerce, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources.
Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, 61 countries and the European Commission to develop a global network that is as integrated as the planet it observes, predicts and protects.
The body of this article is a modified news release from NOAA.
